1. Field of the Invention
The present invention relates to a network interface and more particularly to such an interface for use in translation of coded electrical signals. The invention also relates to methods of constructing such an interface.
2. Related Art
Modern communications networks often comprise a number of layers each of which may include "intelligence". The layers have a hierarchical structure with higher layers making use of functions provided by lower layers to complete assigned tasks. Accordingly an element (or function) in one layer may provide service to an element or function in the layer above and may demand a service from an element or function in the layer below (if any). Thus it is necessary for elements and functions to be able to pass messages between each other. Clearly there has to be some known structure for the messages sent between the layers this structure being known as a message protocol.
Where a complete network is supplied by a single manufacturer, the message protocols are specified by that manufacturer and provided the network does not need to communicate with any other network there is no problem.
However for larger networks, for example for public switched telephony networks (PSTN), it would be unacceptable if the PSTN operator were to be tied to a single manufacturer. Consequently each layer of the PSTN may contain elements from several suppliers, some of which will perform common functions but with a differing message protocol.
Hitherto it has been common practice for the network operator to specify to manufacturers the message protocol to be used by element managers of elements to be incorporated into particular network layers. However, this results in increased costs since each network may require bespoke element manager software to be provided.
An alternative is for the network operator to accept the manufacturers message protocol and to provide bespoke software in the controlling layer. Such arrangements are equally expensive and may lead to inflexibility in the network since it would not be practical to replace an element from one manufacturer with a corresponding element (having a different message protocol) from another manufacturer. The present invention seeks to alleviate the difficulties arising from message protocol incompatibility.